Mod2: CABG SURGERY Flashcards
CORONARY ARTERY BYPASS SURGERY
What’s the purpose of Coronary Artery Bypass surgery?
To promote coronary blood flow to ischemic myocardium
CORONARY ARTERY BYPASS SURGERY
Methods utilized:
Implantation of IMA to epicardial artery w/o ligating branches
Anastomosis of saphenous vein to epicardial artery
Proximal arterial inflow source => ascending aorta
CARDIOPULMONARY BYPASS - DEFINITION
The process of taking venous, or deoxygenated blood, from the right side of the heart to a reservoir where it undergoes oxygenation and returns to arterial circulation to perfuse the rest of the body is known as:
Cardiopulmonary bypass (CPB)
This is the technique where blood is totally or partially diverted from the heart into a machine with gas exchange capacity and subsequently returned to the arterial circulation at appropriate pressures and flow rates
CARDIOPULMONARY BYPASS - DEFINITION
What’s the purpose of performing Cardiopulmonary bypass (CPB)?
To provide the cardiac surgeon with a motionless bloodless field to perform the procedure
To provide artificial ventilation and perfusion
To provide homeostasis under nonphysiologic conditions
To provide protection to vital organs through temperature regulation
CARDIOPULMONARY BYPASS - DEFINITION
Why are bypass technique non physiologic?
Arterial pressure is usually less than normal
Blood flow is non-pulsatile
CARDIOPULMONARY BYPASS - DEFINITION
What’s the overall gaol of CPB?
To maintain oxygenation and perfusion to vital organs
To minimize organ damage by utilizing various degrees of hypothermia
CARDIOPULMONARY BYPASS - DEFINITION
What provider operates the CPB machine?
a Perfusionist
SIX BASIC COMPONENTS OF CARDIOPULMONARY BYPASS
What are the six basic components of the CPB machine?
Tubing
(to bring deoxygenated blood away form patient and oxygenated blood to patient)
Venous reservoir
External Pumps
Heat exchanger
Oxygenator
Arterial Filter
CARDIOPULMONARY BYPASS MACHINE
T/F: All CPB machines look the same
False
There are different types of CPB machine available
CARDIOPULMONARY BYPASS MACHINE
Identify the following components of the CPB machine:
Venous reservoir & blood filter
Membrane oxygenator
Heat exchanger
CPB control console
Roller pump for infusing oxygenated blood
Roller pump for infusing cardioplegia
Roller pump for controlling suction catheters
Cardioplegia reservoir & heat exchanger
A: Venous reservoir & blood filter
B: Membrane oxygenator
C: Heat exchanger
D1: CPB control console
D2: Roller pump for infusing oxygenated blood
D3: Roller pump for infusing cardioplegia
D4: Roller pump for controlling suction catheters
E: Cardioplegia reservoir & heat exchanger
CARDIOPULMONARY BYPASS - VENOUS CANNULATION
What are the three sites for venous cannulation during bypass surgery?
Right atrial appendage
SVC and IVC
Femoral vein
CARDIOPULMONARY BYPASS - VENOUS CANNULATION
What’s the most common site for cannulation during bypass surgery
Single cannulation in the right atrial appendage
Adequate for CABG or Aortic valve surgery
CARDIOPULMONARY BYPASS - VENOUS CANNULATION
Which cannulation option is typically chosen when a more extensive procedure is to be performed?
Two cannulas placed in the SVC and IVC
Used for situations in which complete bypass all of systemic venous return is directed to heart
“Open heart” procedures (MVR, TVR, etc.)
Severe RCA disease (Trying to avoid warm blood entering back into the RA)
Patients in renal failure (When the surgeon wants to reduce the amount of systemic absorption of K+)
CARDIOPULMONARY BYPASS - VENOUS CANNULATION
Which cannulation option is typically chosen either for minimally invasive CABG or redo sternotomy and why?
Femoral vein cannulation
This option is choosen if the pt has had a previous cardiac surgery and the surgeon is concerned about the pt crashing on pump from the possibility of sawing through vessels that are adhered to the thoracic cage?
CARDIOPULMONARY BYPASS - VENOUS RESERVOIR
How is blood drained from the right side of the heart and carried to a venous reservoir?
Occurs by gravity drainage or a vacuum
This is why if “low volume” alarm is heard from the CPB machine, this can be corrected by raising the bed and therefore increasing the distance between the venous reservoir and the level of the heart
CARDIOPULMONARY BYPASS - VENOUS RESERVOIR
Where does blood suctinned from the surgical field collect?
in the Cardiotomy reservoir…
which dumps back into Venous reservoir
Venous reservoir also collects blood from suctions placed in various areas of the heart (Cardiotomy suction, Aortic root suction, L ventricle vent) to maintain a bloodless field for the surgeon
CARDIOPULMONARY BYPASS - VENOUS RESERVOIR
T/F: Fluid and medication can be added here through sampling ports
True
MAIN PUMPS
Once blood is in the venous reservoir, blood is then drawn from the reservoir by
Roller pump, or
Centrifugal pump
MAIN PUMPS
Pumps that compress sections of the tubing along a backplate to propel blood forward are also known as:
Roller pumps
Flow is produced by compressing large-bore tubing in the main pumping chamber as the roller heads turn
Constant nonpulsatile flow is produced that is directly proportional to the number of revolutions/minute
Have hand crank to allow for manual pumping in case power lost
Some are capable of pulsatile flow
MAIN PUMPS
Disadvantages of Roller pump
Economical, but increased destruction of the blood cells
Can entrain air if venous reservoir is allowed to empty
Typically doesn’t happen because of low volume alarms
MAIN PUMPS
A pump that uses an impeller that rotates rapidly, causing a pressure drop that propels the blood sucked into the centrally located inlet into the peripheral circulation is also known as:
a Centrifugal Pump
Magnetically controlled, rapidly rotating impeller that propels blood into the periphery.
Pump flow will change with preload and afterload
Pressure sensitive and must be monitored by a flow meter
Any increase in distal pressure or afterload will cause the flow to decrease and must be compensated for by increasing the pump speed
MAIN PUMPS
What are advantages of Centrifugal pumps over roller pumps?
They do not occlude the tubing that propels blood, so there is less damage to red cells
Less traumatic to blood than roller pumps
MAIN PUMPS
What are disadvantages of Centrifugal pumps?
Nonpulsatile flow
Will not pump if filled with air
Systemic flow pump only, not used in vent or suction rollers
MAIN PUMPS
What is the function of the various pumps present on the CPB machines?
Controls C.O.
Maintains blood flow & perfusion pressures
MAIN PUMPS - Pulsatile vs. Nonpulsatile Flow
Which type of pump allows for pulsatile flow? what are advantages of Pulsatile Flow?
Possible with roller pump, not centrifugal
Improves tissue perfusion
Enhances oxygen extraction
Attenuates release of stress hormones
Results in lower SVR during CPB
Net result => improved renal and cerebral blood flow
MAIN PUMPS - Pulsatile vs. Nonpulsatile Flow
A study that looked at hemodynamics and function during bypass, concluded that non-pulsatile flow lead to increased incidence of acute kidney injury, even when the MAP was maintained WNL during bypass.
Despites this, why is Nonpulsatile flow used more commonly?
Because its easier and still compatible with patient survival
CENTRIFUGLE VS. ROLLER PUMP
How do centrifugal pumps move blood?
Blood is propelled into the impeller
CENTRIFUGLE VS. ROLLER PUMP
How does the roller pump move blood?
Turns and as it turns obstructs the tubing
So you can see how red cells are potentially damaged by the roller pumps
MEMBRANE OXYGENATOR
In the early days of bypass, which types of oxygenators were used?
Bubble oxygenators
MEMBRANE OXYGENATOR
Which oxygenators have replaced bubble oxygenators and why?
MEMBRANE OXYGENATORS
Have since replaced bubble oxygenators
Research began to question bubble oxygenators contribution to postoperative perfusion damage to vital organs
MEMBRANE OXYGENATOR
The blood-gas interface that has a very thin, gas permeable membrane where blood flows around the fibers and oxygen flows through is also known as:
MEMBRANE OXYGENATOR
Coated bundle of hollow microporous polypropylene fibers tightly wound to create a large surface area
MEMBRANE OXYGENATOR
In a membrane oxygenator, where do blood & gas (O2) flows take place?
Blood flows around fibers
Gas (O2) flows through the fibers
MEMBRANE OXYGENATOR
T/F:
Membrane oxygenators contain a Blood-gas interface that allows blood to equilibrate with gas mixtures
True
This is where volatile anesthetics are frequently added
MEMBRANE OXYGENATOR
Arterial CO2 tension during bypass is dependent on:
The total gas flow past the oxygenator
MEMBRANE OXYGENATOR
CO2 levels can be increased or decreased by
Increasing or decreasing oxygen gas flow
(aka increasing/decreasing the “sweep”)
MEMBRANE OXYGENATOR
Where is it placed?
After the centrifugal pump
(MEMBRANE OXYGENATOR)
Before the roller pump
HEAT EXCHANGER
The heat exchanger is made out of?
What’s its function?
Stainless steel tubing
Has water in the inside that can either cool or warm the patient
HEAT EXCHANGER
Benefits of Systemic hypothermia
Myocardial & Neurologic protection
↓ O2 consumption & metabolic requirements of vital organs
For each 1° C ↓in temperature = 8% ↓in metabolic rate
HEAT EXCHANGER
T/F: Blood flows around the tubing and the temperature can be adjusted to a desired level
True
Blood flows around tubes with heated or cooled water flowing through tubes
HEAT EXCHANGER
The heat exchanger also includes a filter that does what?
Catches bubbles that form during rewarming
CATEGORIES OF HYPOTHERMIA
THESE ARE THE CATEGORIES OF HYPOTHERMIA. YOU CAN SEE THAT AS THE TEMPERATURE DECREASES, THE SAFE ARREST TIME …
INCREASES
MEANING LONGER TIMES ARE TOLERATED WITH COLDER DEGREES
CATEGORIES OF HYPOTHERMIA
THE PROCESS BY WHICH THE PATIENT IS COOLED TO 18-28 D CELCIUS FOR AORTIC ROOT REPAIR is also known as:
CIRCULATORY ARREST
CATEGORIES OF HYPOTHERMIA
DURING CIRCULATORY ARREST, THE BYPASS MACHINE IS..
STOPPED!!!
SO THE SURGEON CAN MAKE THE GRAFT REPAIRS TO THE AORTIC ROOT
CATEGORIES OF HYPOTHERMIA
THE MAXIMAL TIME FOR ARREST IS TYPICALLY AROUND…
16-20 MINUTES
CATEGORIES OF HYPOTHERMIA
IT’S IMPORTANT TO NOTE THAT TEMPERATURES CANNOT BE ABRUPTLY INCREASED AFTER HYPOTHERMIA. Why not?
THERE IS A HIGH PROBABILITY OF PRODUCING GASEOUS MICROEMBOLI WHEN TEMPERATURES ARE INCREASED TOO QUICKLY
This is the case BECAUSE GAS SOLUBILITY DECREASES AS BLOOD TEMPS RISE
CATEGORIES OF HYPOTHERMIA
Rewarming too quickly can also cause…
Neurologic damage, and
Bypass afterdrop
CATEGORIES OF HYPOTHERMIA
The Bypass afterdrop is thought to be a result of…
Inadequate total body warming while on bypass
Causes a redistribution of heat from the warmer core to the cooler shell tissue after weaning from bypass
CATEGORIES OF HYPOTHERMIA
AS YOU RECALL IN THE FIRST LECTURE WE MENITIONED HOW ——- WAS THE IDEAL PLACE TO MONITOR TEMPERATURE.
THE ARTERIAL INFLOW to the patient
Can also be called Arterial outflow from the CPB machine
CATEGORIES OF HYPOTHERMIA
TEMPERATURE GRADIENTS BETWEEN THE ARTERIAL OUTLET (machine to pt) AND VENOUS INFLOW (pt to machine) SHOULD NOT EXCEED…
10 DEG CELCIUS
(8˚C in pediatrics)
Reason why monitor temperature at multiple sites to ensure uniform cooling and rewarming
CATEGORIES OF HYPOTHERMIA
HYPOTHERMIA generally used for straight forward/routine open heart procedures is categorized as:
Mild to moderate hypothermia
Degrees: 32-37C (Mild), 28-32C (Moderate)
Safe arrest time: 4-5”(Mild), 8-10”(Moderate)
CATEGORIES OF HYPOTHERMIA
What’s the temperature range and Safe arrest time for Deep hypothermia?
Degrees: 18-28˚C
Safe arrest time: 16-20”
CATEGORIES OF HYPOTHERMIA
HYPOTHERMIA used for complicated adult procedures (arch vessels) is categorized as:
Profound hypothermia
Degrees: 14-18˚C
Safe arrest time: 64-84”
ADDITIONAL COMPONENTS
Additional components to the bypass machine include:
Arterial Filters
Cardiotomy
Basket Suction
Aortic Root Suction
LV vent
Gas blender & flow meter
Arterial line pressure monitor
Temperature sensors
Anesthesia vaporizers
Ultrafiltration/Hemoconcentrator
ADDITIONAL COMPONENTS
Where are arterial filters located?
In the tubing just before systemic circulation
Typically place here between the oxygenator and pt as a last chance to remove emboli and air
ADDITIONAL COMPONENTS
What’s the purpose of the Cardiotomy?
Drains blood back into the venous Reservoir
ADDITIONAL COMPONENTS
There are multiple suctions to remove blood from the field. These suctions include:
Basket suction
Aortic root suction
LV vent
ADDITIONAL COMPONENTS
What’s the purpose of the LV vent?
Prevents LV distension, by
keeping it decompressed during the cross clamp period
ADDITIONAL COMPONENTS
What could cause LV distention?
Aortic insufficiency and
Venous drainage from the thebesian and bronchial veins
Could lead to increasing wall tension, which
Prevents subendocardial cardioplegia distribution
Ultimately could result in myocardial ischemia
ADDITIONAL COMPONENTS
What’s the purpose of Gas blender & Flow meter?
Used to maintain appropriate O2 saturation levels and
Respiratory acid-base homeostasis
ADDITIONAL COMPONENTS
What’s the purpose of Temperature sensors?
Monitor arterial, venous, & cardioplegia temperatures
ADDITIONAL COMPONENTS
What’s the purpose of Ultrafiltration/Hemoconcentrator?
Counteracts hemodilution
Increase hematocit without transfusion
Removes excess volume through dialysis or centrifugal separation of fluid and plasma components from the circulating blood volume
ARTERIAL CANNULA
What’s the purpose of the Arterial cannula?
Brings oxygenated blood back to the pt’s systemic circulation via the aorta
ARTERIAL CANNULA
Where is the arterial cannula placed?
Placed in the ascending aorta
Distal to cross clamp
Proximal to brachiocephalic/innominate artery
ARTERIAL CANNULA
Which cannula is always the first cannula placed and the last cannula to be removed?
The arterial or aortic cannula
ARTERIAL CANNULA
Why is the arterial/aortic cannula always the first cannula placed and the last cannula to be removed?
In the event of an emergency, the pefusionist can temporarily initiated bypass with single aortic cannulation
ARTERIAL CANNULA
Why is “crashing onto bypass” short lived?
As the bypass machine reserve risks will be depleted, central venous cannulation must eventually be acheived
ARTERIAL CANNULA
The surgeon will also request that blood pressure be dropped to a systolic pressure below 100 or a MAP below 60. Why?
To reduce the chance of causing aortic dissection
ARTERIAL CANNULA
Besides the ascending aorta, in what other vessel could the arterial cannula be placed?
Femoral artery
Axillary artery
Subclavian artery
CARDIOPLEGIA CANNULA
After the cross clamp is placed, the cardioplegia cannulas are placed. Where are the cardioplegia cannulas placed?
Ascending aorta
Proximal to cross clamp
This is called Antegrade cardioplegia
Note that the coronaries are situated in the aortic root just outside the aortic valve
Cardioplegia travels antegrade down the coronaries, which follows normal blood flow
CARDIOPLEGIA CANNULA
What’s the purpose of the cross clamp?
Prevents systemic absorption of the cardioplegic solution
CARDIOPLEGIA CANNULA
After the cross clamp is placed, the cardioplegia cannulas are placed proximal to the cross clamp to deliver what?
Potassium-rich solution to the heart
This induces diastolic arrest while the surgeon works on the heart
CARDIOPLEGIA CANNULA
Besides the ascending aorta, where else can the cardioplegia cannula be placed?
In the Coronary sinus
This is called retrograde cardioplegia
Recall that coronary sinus is the where great veins dump deoxygenated blood back into the RA
CARDIOPLEGIA CANNULA
Which cardioplegia approach provides greater myocardial protection and is especially important in high grade coronary obstruction?
Retrograde cardioplegia
Accessed via SCV
CARDIOPLEGIA CANNULA
T/F: During CABG, Cardioplegia can also be delivered into vein grafts for extra protection
True
CARDIOPLEGIA
A hyperkalemic crystalloid solution that can either be crystalloid-based or blood-based.
What’s Cardioplegia?
Hyperkalemic crystalloid solution
Can be crystalloid-based or blood-based
CARDIOPLEGIA
How does the use cardioplegia provide myocardial preservation?
By putting the heart in a diastolic cardiac arrest
also known as a depolarized arrest
CARDIOPLEGIA
Explain how Cardioplegia causes Diastolic or Asystolic depolarized arrest
Going back to the fast action potential, we know that hyperkalemia causes the cell membrane to become less negative
When K+-rich cardioplegia surrounds the myocyte, it increases the RMP from -90mV to -60mV to -40mV which we know is threshold
That initiates a chemical AP
This causes Na+ channels to become inactive, and also cause Diastolic or Asystolic depolarized arrest
CARDIOPLEGIA
Cardioplegia can also be given either cold or warm, but why do some studies say that hypothermic cardioplegia may not be needed?
Normothermic arrest will decrease O2 consumption by more than 90%
CARDIOPLEGIA
How would adding cold solution to normothermic arrest affect O2 consumption?
Will decrease O2 consumption by more than 97%
CARDIOPLEGIA SOLUTION
Cardioplegia solution varies from institution to institution
Cardioplegia can be —- based or —- based.
Either Blood or crystalloid
Blood becoming more common, increases O2 carrying capacity
CARDIOPLEGIA SOLUTION
When will the surgeon request that the perfusionist begin giving cardioplegia?
Following the initiation of cardiac bypass
After the aortic cross clamp is placed
This causes that reduction in the membrane potential
And eventually the heart will stop
CARDIOPLEGIA SOLUTION
T/F: As previously mentioned, either cold or warm cardioplegia is given
True
CARDIOPLEGIA SOLUTION
When cold cardioplegia is given, why must it be given every 15-20 minutes?
Gradual washout and Rewarming of the myocardium will occur
Which will increase its risk of ischemic injury
CARDIOPLEGIA SOLUTION
Temperature of Cold cardioplegia
10-15˚c
CARDIOPLEGIA SOLUTION
Activity of which monitor may indicate need for additional cardioplegia
EKG
CARDIOPLEGIA SOLUTION
Why does the cardioplegic solution also contains other components?
To help prevent the accumulation of metabolites
To make the solution slightly hypertonic to reduce edema
CARDIOPLEGIA SOLUTION
Other components found in the cardioplegic solution include:
Na+, Ca+, Mg+
Mannitol and/or albumin
NTG (coronary dilator)
HCO3 (buffer)
Glucose (cellular energy)
Hbg (O2-carrying)
Lidocaine or procaine (membrane stabilization)
CARDIOPLEGIA SOLUTION
Why does the cardioplegic solution only containd Small amounts of calcium?
To control excessive intracellular influx of Ca2+
CARDIOPLEGIA SOLUTION
What could happen if the cardioplegic solution contained higher levels of Ca++?
Could cause the heart to arrest in systole
Ca++ causes contraction
And that would drastically increase O2 demand
CARDIOPLEGIA SOLUTION
Why is Mannitol added to the cardioplegic solution?
To control cellular edema
CARDIOPLEGIA SOLUTION
Why are energy substrates added to the cardioplegic solution?
To assist the heart in the production of ATP for energy
PUMP PRIMING SOLUTION
Prior to its use, why is the bypass pump primed with fluid?
To get rid of air bubbles
Deairing & priming of pump circuit
PUMP PRIMING SOLUTION
What is the main cause of hemodilution?
Volume of Priming Solution
While it attempts to mimic the composition of blood,
The increase volume dilutes not only the proteins in the blood, but also plasma levels of drugs
PUMP PRIMING SOLUTION
What must be considered when choosing a priming solution?
Osmolarity
Electrolytes
Pt’s preop HCT, and
Overall volume of the circuit
PUMP PRIMING SOLUTION
The perfusionist must calculate the pt’s estimated HCT after the pt’s blood is mixed with the priming solution; why?
If dilution is Not anticipated, the pt’s depth of anesthesia and circulating drugs may be reduced during bypass
Volume of distribution must be estimated to prevent reduced depths of anesthesia and circulating drug levels
PUMP PRIMING SOLUTION
The most commonly used priming solutions are Crystalloids. What are their main benefits?
Cheaper!!!
Anaphylactic reactions voided
Easy to handle
Improved postoperative pulmonary & renal function
PUMP PRIMING SOLUTION
What are disadvantages of Crystalloid priming solutions?
Unable to preserve colloid pressure
This could lead to Post-op Pulmonary Edema
Addition of albumin offsets this
PUMP PRIMING SOLUTION
What are risks associated with colloid priming solutions?
ALLERGIC REACTIONS
Similar effects to albumin
ADVERSE EFFECT ON BLOOD COAGULATION
Expensive!!!
PUMP PRIMING SOLUTION
Why would Heparin be added to the pump priming solution?
Ensure safety level of anticoagulation
PUMP PRIMING SOLUTION
Why would Mannitol be added to the pump priming solution?
To Promote diuresis
PUMP PRIMING SOLUTION
Why would NaHCO3 be added to the pump priming solution?
(Buffer?!!!)
PUMP PRIMING SOLUTION
Why would Antifibrinolytics (Amicar) be added to the pump priming solution?
Acts as an inhibitor of fibrinolysis
PUMP PRIMING SOLUTION
Why would Calcium be added to the pump priming solution?
To prevent hypocalcemia due to citrate in transfused blood
PUMP PRIMING SOLUTION
Why would Corticosteroids be added to the pump priming solution?
Anti-inflammatory
PUMP PRIMING SOLUTION
Why would Blood be added to the pump priming solution?
If patient is starting off with a low hematocrit
PUMP PRIMING VOLUME
At the onset of bypass, the pump must be “tested” to ensure that:
It Works!!!
Pressures from both the arterial and venous side will be checked
PUMP PRIMING VOLUME
At the onset of bypass, the pump must be “tested” to ensure that it works. Pressures from both the arterial and venous side will be checked.
During that time, the fluid used to prime the machine will then be mixed with:
the patient’s blood
PUMP PRIMING VOLUME
At the onset of bypass, the pump must “tested” to ensure that it works. Pressures from both the arterial and venous side will be checked.
During that time, the fluid used to prime the machine will then be mixed with the patient’s blood, causing:
Hemodilution
Which reduces blood viscosity in preparation for the hypothermia
PUMP PRIMING VOLUME
Hemodilution can cause the hematocrit to fall to about which range?
22-27%
PUMP PRIMING VOLUME
The goal is to maintain a HCT >
21%
Trend is to maintain HCT > 21%
PUMP PRIMING VOLUME
While normal hemodilution is tolerated, what is a possible outcome of excessive hemodilution?
Reduce oxygen carrying capabilities
PUMP PRIMING VOLUME
What’s the average pump priming volume?
1.5 to 2.5 L
PUMP PRIMING VOLUME
Some degree of anemia is desirable; why?
Offsets changes in blood viscosity due to hypothermia
PHYSIOLOGIC EFFECTS OF CPB
What are positive effects of Hypothermia during bypass?
Reduces tissue metabolism & O2 consumption
Improves myocardial protection
Provides organ protecting during low flow states
Provides end-organ protection (liver, brain) in case of low-flow negative effects
Reduces anesthetic requirements (↓ awareness)
PHYSIOLOGIC EFFECTS OF CPB
What are negative effects of Hypothermia during bypass?
Shifts Oxyhemoglobin curve to Left » impairs tissue O2 release
Which reduces oxygen delivery to tissue
Impairs platelet function and coagulation
Reduces serum ionized [Ca2++]
↑ SVR
PHYSIOLOGIC EFFECTS OF CPB
Shifts Oxyhemoglobin curve to Left » impairs tissue O2 release. This could be Offset by:
↑ O2 solubility at lower temperatures & lower metabolic demands
PHYSIOLOGIC EFFECTS OF CPB
T/F:
While bypass does provide protection to vital organs, it is also a/w some negative side effects
True
PHYSIOLOGIC EFFECTS OF CPB
Many negative physiologic effects of bypass are related to increase
in —– hormone, and ——-
Stress hormone, and
Systemic inflammatory responses
PHYSIOLOGIC EFFECTS OF CPB
The release of these stress hormones can cause:
Tissue injury
PHYSIOLOGIC EFFECTS OF CPB
During bypass, there is an elevated level of circulating catecholamines, cortisol, vasopressin, and angiotensin. Levels of these hormones can be influenced to some degree by:
Depth of anesthesia
Type of surgical repair
Presence of pulsatility during bypass
PHYSIOLOGIC EFFECTS OF CPB
What substances are released during a Systemic Inflammatory Response Syndrome (SIRS)?
Endotoxin
Tumor necrosis factor
Anaphylatoxins
Cytokines
Neutorphils
PHYSIOLOGIC EFFECTS OF CPB
What’s the physiologic effect of substances released during SIRS?
Tissue injury in many organs
(brain, lungs, kidneys, heart)
PHYSIOLOGIC EFFECTS OF CPB
T/F: supraventricular and ventricular arrhythmias can occur right after bypass and must be immediately treated
True
PHYSIOLOGIC EFFECTS OF CPB
Usually if patients are in a ventricular arrhythmia, the surgeon will use —- to defib the heart.
Internal pads
V-tach and V-fib should be treated immediately
=> internal pads 10-30 J
PHYSIOLOGIC EFFECTS OF CPB
What’s the most common arrythmia seen around cardiopulmonary bypass?
Atrial fibrillation
Usually develops 2-5 days postop
PHYSIOLOGIC EFFECTS OF CPB
How is A-Fib treated in the immediate post-op phase?
Synchronized cardioversion
Especially if the pt was in sinus rhythm before surgery
PHYSIOLOGIC EFFECTS OF CPB
What’s the drug of choice to treat A-fib caused by CPB?
Amiodarone
PHYSIOLOGIC EFFECTS OF CPB
Metabolic disturbances commonly seen include:
Hypokalemia (vNa+)
Hyperkalemia(^Na+)
Hypocalcemia (vCa2+)
Hyperglycemia (^Glucose)
PHYSIOLOGIC EFFECTS OF CPB
What are causes of Hypokalemia seen during bypass?
Preoperative diurectics
Mannitol administration during bypass
Treatment of hyperglycemia with insulin
PHYSIOLOGIC EFFECTS OF CPB
What are causes of Hyperkalemia seen during bypass?
Large doses of cardioplegia
Impaired renal function
Respiratory or metabolic acidosis
PHYSIOLOGIC EFFECTS OF CPB
What are causes of Hypocalcemia seen during bypass?
Blood transfusion
(Citrate)
PHYSIOLOGIC EFFECTS OF CPB
Hyperglycemia is extremely common after bypass. What are its causes?
Use of glucose-containing cardioplegic solutions
Use of exogenous catecholamines
Surgical stress
The society of thoracic surgeons recommends keeping glucose levels <strong><180 mg/dl</strong> in order to reduce morbidity and mortality associated with hyperglycemia follwing bypass surgery
PHYSIOLOGIC EFFECTS OF CPB
Despite heparin reversal, pts oftentimes suffer from bleeding and coagulopathies. Oftentimes, the bleeding is due to:
Inadequate surgical hemostasis
Hemodilution
Platelet dysfunction
Fibrinolysis
PHYSIOLOGIC EFFECTS OF CPB
What are causes of Platelet dysfunction?
Platelet activation and consumption
Clumping and degranulation after contact with bypass apparatus
Reduction in number (thrombocytopenia), adhesiveness, and aggregation
<em>Platelet number and function is often decreased after CPB</em>
PHYSIOLOGIC EFFECTS OF CPB
Pulmonary Complications during bypass include:
Atelectasis
Decreased arterial oxygenation
Bronchospasms
Hemo and Pneumothorax
Pulmonary Edema
PHYSIOLOGIC EFFECTS OF CPB
What’s a common cause of decreased arterial oxygenation?
Atelectasis
Can be improved with recrutment maneuvers
PHYSIOLOGIC EFFECTS OF CPB
Decreased pulmonary blood flow during bypass could lead to:
V/Q mismatch
PHYSIOLOGIC EFFECTS OF CPB
What’s responsible for ↑ PVR (lungs normally inactivate)?
Lack of degradation of catecholamines during CPB
Leads to ↑ catecholamines
Which results in ↑ PVR (lungs normally inactivate)
PHYSIOLOGIC EFFECTS OF CPB
Why must the potential for awareness in patients be especially assessed ?
Occurs more frequently in cardiac surgery
PHYSIOLOGIC EFFECTS OF CPB
Why is the chance of experiencing awareness higher during the rewarming phase?
Hypothermia reduces cerebral metabolic demands on bypass
This decreases anesthetic requirements and awareness
Patients have a higher chance of experiencing awareness during the rewarming phase
PHYSIOLOGIC EFFECTS OF CPB
Awareness is more frequent in cardiac surgery than others; especially during the rewarming phase. Caution should always be used during this time. What could provider do to ease the concern for awareness?
Consider time since last sedative-hypnotic administration
Consider administering sedative or hypnotic medication, especially in younger pts
PHYSIOLOGIC EFFECTS OF CPB
How does CPB affect Renal blood flow and tubular function?
Renal blood flow and tubular function are decreased during CPB
PHYSIOLOGIC EFFECTS OF CPB
T/F: Postoperative renal failure requiring dialysis is common
False
Postoperative renal failure requiring dialysis is Not common
(2-5%)
PHYSIOLOGIC EFFECTS OF CPB
When Postoperative renal failure requiring dialysis occurs following bypass surgery, which groups are most affected?
The elderly
Those with pre-existing renal dysfunction
Long duration of bypass
Post operative low output syndrome
PHYSIOLOGIC EFFECTS OF CPB
About what percentage of patients experience one or more complications?
20%
PHYSIOLOGIC EFFECTS OF CPB
Why is it important to identify patients with a history of renal failure?
For medication metabolism and excretion
Could explain hyperkalemia post bypass
PHYSIOLOGIC EFFECTS OF CPB
What are consequences of Renin-angiotensin-aldosterone system alterations?
Promotes increased renal vascular resistance
Promotes Na+ and H20 retention
Leads to decreased renal blood flow, GFR, and tubular function
PHYSIOLOGIC EFFECTS OF CPB
How does Hemodilution protects the kidneys?
Increases cortical plasma flow
PHYSIOLOGIC EFFECTS OF CPB
Hemoglobinuria may result from:
Long bypass runs (> 4hrs)
This could lead to ARF
PHYSIOLOGIC EFFECTS OF CPB
How does CPB affect cerebral autoregulation values?
CPB is associated with Lowers cerebral autoregulation values
PHYSIOLOGIC EFFECTS OF CPB
Embolic phenomena during bypass come from:
Fat
Thrombi
Platelets
Foreign substances
Air/gas
PHYSIOLOGIC EFFECTS OF CPB
Why should you keep blood glucose levels <180 mg/dl?
To prevents cerebral ischemic episodes
PHYSIOLOGIC EFFECTS OF CPB
The absence of significant postoperative morbidity related to CPB depends primarily on each particular patient’s ability to:
Compensate for the physiologic derangements induced by CPB
